Le 13 avril 2023, Madame Nguyen Thi Hue a soutenu sa thèse de doctorat à l'USTH, Hanoi, dans la spécialité Biotechnologies Pharmacologiques, Médicales et Agronomiques.
Sa thèse intitulée Histological and molecular mechanism analysis of the incompatible interaction between Meloidogyne graminicola and Oryza sativa L. a été dirigée par Stéphane Bellafiore (IRD, UMR PHIM) et le Prof Ha Viet Cuong (VNUA).
Le jury était composé comme suit :
- Assoc. Prof. Eric Lacombe, USTH - Président du Jury
- Prof.Pierre Czernic, University of Montpellier - Rapporteur
- Assoc. Prof. Nguyen Xuan Canh, Vietnam Academy of Agriculture - Rapporteur
- Assoc. Prof. Tran Dang Khanh, Agricultural Genetics Institute - Rapporteur
- Dr. Pham Thi Dung, Vietnam Academy of Agriculture - Examinateur
- Dr. Mai Thi Phuong Nga, USTH - Examinateur
- Dr. To Thi Mai Huong, USTH - Examinateur, Secrétaire de soutenance
Toutes nos félicitations à Madame Nguyen Thi Hue !
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Résumé de la thèse (en anglais)
Meloidogyne graminicola (Mg) is a biotrophic plant parasitic nematode which is considered as the major nematode affecting rice production in Southeast Asia. Zhonghua 11 is an Oryza sativajaponica rice variety resistant to this pathogen. This research focuses on the underlying molecular, cellular and genetic studies of the incompatible interaction between Zhonghua 11 and Mg. The inheritance determinism of the resistant gene(s) in Zhonghua 11 was investigated using F2 progenies obtained from intraspecific (O. sativa japonica Zhonghua 11 x O. sativa japonica Nipponbare) and interspecific (O. sativa japonica Zhonghua 11 x O. sativa indica IR64) crosses. The results indicate that resistance in Zhonghua 11 is likely controlled by two unlinked dominant genes. Using the histological approach, we found that the resistance in Zhonghua 11 is associated with hypersensitivity response. We also studied the possible involvement in this observed incompatible interaction of several autophagy genes, and of three classical defence hormone-related pathways (i.e. salicylic acid (SA), jasmonic acid (JA), and ethylene (ET)). The result showed that SA signalling may be important in the resistance-mediated hypersensitive response in the Zhonghua 11. Notably, the expression of OsAtg4 and OsAtg7 significantly increase in roots of resistant plant in parallel with the cell death response, suggesting that autophagy is activated and may contribute to the resistance -mediated hypersensitive response.
The Zhonghua 11 resistance durability is however potentially threatened by the evolution of Mg that can bypass the resistance mechanism and become virulent. We survey in a natural infested field for endogenous Mg populations and isolated a Mg pathotype virulent to Zhonghua 11. Using morphology and molecular analysis, we confirmed that the virulent pathotype is a Mg. Comparison with an avirulent pathotype revealed few morphometric specificities of the virulent one. Reproduction factor measurement on different rice varieties showed that this virulent Mg pathotype has a high aggressiveness on Zhonghua 11 but also against two others of Oryza sativa resistant rice varieties namely LD24 and Khao Pao Maw. Examination of the reproductive factor of Mg on several cover crop species showed that the pathogen could significantly reproduce on those plants. Furthermore, we showed that the Mg substantially reduces rice development, rice seed germination, and rice seed vigor.